John Miles has spent much of his life’s work focused on a very complex question: “How can we balance the conflicting needs of providing affordable energy and transportation for all, advancing society, and protecting our planet?” As transportation consumes a good percentage of the world’s energy resources and generates more than half of the world’s emissions, he has always had a keen interest in radical transportation alternatives. John has helped pioneer energy and transportation system projects in his 40+ year career with UK-based engineering and consulting firm Arup. These days, he splits his time between consulting on transportation strategy with Arup and a post as Professor of Engineering at Cambridge University where he and his students research approaches to the same complicated question. As part of our series on sustainable transportation, we asked John to share his ideas on how transportation can become more sustainable in the next two decades and beyond.

H1: Global CO2 emissions from transport could increase 60% by 2050. How can industry leaders look to curb this trend, especially as population skyrockets?

John: People say traveling is bad because it produces emissions and it consumes vast quantities of resources. But, if you could have a form of travel that didn't consume so many natural resources, and didn’t produce so many emissions well then there's nothing wrong with travel. Indeed, movement is part of our modern life.

Mobility demands inevitably are going to rise around the world. Roughly one and a half billion people in the world have a reasonable standard of living and about five and a half billion people don't. If the standard of living rises for those five and a half billion over the next 20 or 30 years then the demand for transport will just skyrocket.

If we can’t curb travel and needs are growing, what do we do? I’m speaking a bit simplistically, but we need to do everything we can to move our general means of mobility so that it is powered by the wind and the sun, because that's the only way that we'll reduce transport emissions. Anything you can do to electrify transport and generate that electrical power from renewable sources is key. Because, if we produce electricity from dirty sources we haven't done much good. Renewable energy resources for transportation are critical, but renewables will only address part of our problem.

H1: If moving towards transport solutions powered by renewable energy will only address part of the challenge, what else can we do?

John: When you see numbers comparing carbon footprints among cars and buses and trains the saying goes that cars are worse, buses are better, and trains are best. If you look more closely at these comparisons, however, the old saying is not all that accurate.

It is only true when the bus is full and when the train is full. If you have a full bus, then the amount of carbon you produce per passenger mile is much lower than it is for a car. But if you have a full car and a half-empty bus, the energy consumption of the car is better than the bus, and the same goes for a train. It all boils down to the occupancy ratio, or load factor, and this is by far the biggest issue in transport sustainability. In the future we need to develop transport systems which can adapt continuously to the levels of demand – systems which can adjust their capacity during the working day to ensure that the load factors are always very high. We might call this process ‘dynamic capacity matching.’

Now, this is very difficult for a train. If you look at the optimal number of energy consumption for trains you get about 30 grams of CO2 per passenger kilometer. But, if the train is only 10-20% occupied, as they often are in the off-peak hours, you start running up to numbers like 150-180 grams of CO2 per passenger kilometer, and that's very bad. When you average over a typical working day, the train is often almost as bad as a car (typically 80-90 grams of CO2 per passenger kilometer). So, what we want are vehicles that have variable capacity so that during the peak hours they can carry 150-200 hundred people and during mid-day carry only 20-30 people.

H1: How do you foresee Hyperloop helping with capacity?

John: I think Hyperloop has a fantastic future because it consists of a series of relatively small, independent, pods with maybe 20-50 people per pod. During busy times, you can have lots of pods zipping around, and during slow times a lot of those pods could be just sitting by the wayside not doing anything and not consuming energy.

This approach is very unlike today’s transport. A bus with 60 seats on it runs whether it has 2, 30, or 60 people. With trains, you can decouple a couple of carriages during the working day, but that isn’t very convenient. If you've got four or eight carriages on the train that's what trundles round all the time more or less.

Hyperloop pods are independent. They get deployed autonomously when there is demand, so it's very straightforward to create variable capacity. A Hyperloop is a variable capacity mass transit system, and that’s something we've never had before.

Normally a system like that is very inefficient and traditionally unaffordable. To have lots of small things running around, picking people up and dropping them off, you need to have lots of drivers and you have to pay for all these drivers. But because Hyperloop is an autonomous system, you can have as many vehicles as you like and if they're sitting doing nothing in the middle of the day when it's not very busy, it doesn't cost you a penny in staff costs.

H1: Technical advancements are creating more connected, intelligent transport systems. What other trends do you see that can help drive greater capacity?

John: If you're going to have efficient use of energy and low production or emissions per passenger then you have to have fewer vehicles and have shared transportation. Shared transportation is always difficult because people want to go to different places. So, trying to get 10-20 people on the same vehicle going to the same location has always been very difficult.

But, with today's levels of communications, information technology, and social media it is now a thousand times easier than it used to be. I believe you will soon see intelligent systems that can gather blocks of people who want to go from one place to another and are willing to share transportation and then send vehicles to pick them up. This is what’s known as demand-responsive transport, and it’s all about the bus coming to pick you up rather than you going to find the bus stop. Demand-responsive transport has the potential to shift the public perception of public transportation entirely. I think that's a huge deal.

H1: As standards of living improve and transport demand increases for the five and a half billion who aren’t traveling as much as those in developed countries, what do you see as the biggest opportunity to establish sustainable transport?

John: We have to do everything we can to help developing countries travel by cleaner methods. So, we need electric cars, electric buses, Hyperloop, electric trains, and green energy generation. Those are the things that we have to do. The real key to this is money. And, right now, most of these green transport and energy systems, including electric cars, cost more than conventional vehicles. So, our challenge is to produce these nice green systems at a price we can afford.

That's why I like Hyperloop so much. I must say at first I was a disbeliever of Hyperloop. What changed my mind was the realization that it is a lightweight, small system. Because the fixed infrastructure forms the largest part of the cost of a mass transit system, reducing the scale of the infrastructure is about the best thing you can do to reduce costs. This gives Hyperloop a massive advantage over conventional and high-speed rail systems. If you add to that its ability to offer ‘dynamic capacity matching’ and incredibly fast, frequent, services, it becomes a clear winner. If the system can be demonstrated to work, and if you are starting from a blank sheet of paper in an emerging economy, why would you build anything else as your national transportation infrastructure?